Heavy ion irradiation induced dislocation loops in AREVA’s M5® alloy

Abstract

Heavy ion irradiation induced dislocation loops in AREVA's M5 alloy Cover letter for the second revised submission of the article to the Journal of Nuclear MaterialsPressurized water reactor (PWR) Zr-based alloy structural materials show creep and growth under neutron irradiation as a consequence of the irradiation induced microstructural changes in the alloy. A better scientific understanding of these microstructural processes can improve simulation programs for structural component deformation and simplify the development of advanced deformation resistant alloys. As in-pile irradiation leads to high material activation and requires long irradiation times, the objective of this work was to study whether ion irradiation is an applicable method to simulate typical PWR neutron damage in Zr-based alloys, with AREVA's M5 ® alloy as reference material. The irradiated specimens were studied by electron backscatter diffraction (EBSD), positron Doppler broadening spectroscopy (DBS) and in-situ transmission electron microscopy (TEM) at different dose levels and temperatures. The irradiation induced microstructure consisted of <a>-and <c>-type dislocation loops with their characteristics corresponding to typical neutron damage in Zr-based alloys; it can thus be concluded that heavy ion irradiation under the chosen conditions is an excellent method to simulate PWR neutron damage.As recommended by the editor, the abstract has been shortened. Heavy ion irradiation induced dislocation loops in AREVA's M5 alloy Detailed Response to the reviewersThe authors want to thank the reviewers for their helpful and detailed comments.The following changes have been made in the revised article, based on the reviewers' suggestions:General Changes: The units for flux and fluence have been converted from cm^-2 to m^-2. Reviewer 1: The labelling of the sections and subsections in the text has been corrected.  While a difference in positron lifetime measurements between single vacancies and vacancy clusters can be resolves with positron lifetime measurements, it is more difficult to decide whether the difference would be reflected in the Doppler broadening spectroscopy signal. Therefore, all passages implicating such a correlation have been removed or reworded, as recommended by the reviewer.  The reference for 0.3wt.% of Nb in solution has been added.  The references have been re-ordered to appear in the right order.  A schematic of the EBSD specimen cutting process has not been included; however, the specimen preparation description has been revised to make it more comprehensible.  The typing error of 6450°C annealing temperature has been corrected.  The diffraction vector for the <a>-loop observation was (11-20) and not (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) as was incorrectly stated in the draft; the error has been corrected.  The interpretation of the additional reflexes in sample A1 after irradiation has been reworded. A more detailed explanation is given why oxidation is not assumed to be the cause of the changes.  A ...

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Effect of Xe26+ ion irradiation on the microstructural evolution and mechanical properties of Zr–1Nb at room and high temperature

“…In M5 alloy irradiated by 1 MeV Kr ions the size and density of hai-type dislocation loops increase with dose at 573 K from 0.1 to 17 dpa. In addition, hci-type dislocation loops are not present until at the dose of 6.8 dpa [5]. It was discussed above that the study by Yamada and Kameyama [6] showed that high temperature of 673 K enhances the formation of hci-type dislocation loops.…”

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